Connecting 12V RV cable aviation plug into 12V/25A DC Output of AC200P

It is my understanding that the 12V RV cable aviation plug 2 pin male should plug into the 12V/25A DC Output 2 pin female port of the AC200P. It seems like female plug has 3 plastic elements that block the male 12V RV cable from pushing in even when lining up the pins and pulling back the outer black metal sleeve of 12V cable. The 12V aviation plug cable outer black metal sleeve is not threaded when the female 12V port is threaded. This connection makes no sense. Can you please provide info on how to connect into this 12V/25A DC output?